People often communicate with each other by message—e.g., via the Short Message Service (SMS) commonly associated with phones, or via various instant messaging (IM) systems. In the past, SMS was effectively the only way to send a text message from a cell phone. SMS messages are generally sent between devices that have phone numbers. These messages are subject to strict size limits, and the sending of such messages is charged by phone carriers at SMS-specific rates. However, many modern cell phones have Internet connectivity and the ability to participate in a wide variety of communication protocols, such as Hypertext Transfer Protocol (HTTP). HTTP has the ability to send transmit content that has a wide variety of features (e.g., links, photos, audio, etc.) and arbitrary length. Additionally, an HTTP message can be sent between any devices that are addressable on the Internet. Such messages are sent using the devices' ordinary Internet service (thereby avoiding the use of SMS-specific pricing, and avoiding any limitations associated with IM systems).
While message sent via HTTP are often more convenient, offer richer content, and are more economical to send, SMS and IM continue to have legacy influence. Many phones have Internet service and can communicate by HTTP, but nearly all phones have SMS. When one person wants to send a message to another, the user often does not know what capabilities are available on the recipient's phone, so the sender often sends an SMS message in order to be able to reach the recipient without regard to what type of device the recipient has. But the decision to use SMS subjects the message to SMS's limitations.